The present invention relates generally to an actuator, and more particularly to a control device applicable to an actuator. The control device is an integration of a limit switch control circuit and an input voltage detection circuit and has electronic brake effect.
Most of the conventional limit switches applied to actuators pertain to hidden-type mechanical limit switches. FIG. 1 shows a conventional control device for an actuator 1. An actuating member 3 of the actuator 1 is driven by a motor 2 to move axially and reciprocally. Two mechanical limit switches 4, 5 are arranged in fixed positions to restrict the travel of the actuating member 3 within a range between two dead ends. In such conventional control device, the limit switches 4, 5 are hidden in the actuator so that it is impossible to adjust the positions of the limit switches 4, 5 in accordance with actual requirements. Moreover, the current that drives the motor 2 will directly flow through the limit switches 4, 5. As a result, a high current may flow through the contacts of the limit switches 4, 5 to cause damage of the contacts. Also, after a long period of use, the contacts are liable to damage. Moreover, the limit switches 4, 5 are very likely to be directly collided by external objects and damaged.
FIG. 2 shows another conventional control device for an actuator 1. The positions of the limit switches 4′ and 5′ of the control device are freely adjustable. However, in such control device, the circuit of the motor 2′ must be connected to the limit switches 4′ and 5′ by external connection wires. Therefore, as a whole, the layout of the external wires of the actuator 1′ is complicated. This will affect the appearance of the actuator 1′ and cause a security concern with the use of the actuator 1′. Furthermore, the limit switches 4′ and 5′ need to control the operation of the motor 2′ through additional control circuit 6′. This leads to increase of cost.
FIG. 3 shows still another conventional control device for an actuator 1″. In this control device, neither the motor nor the limit switch control circuit 7″ of the actuator 1″ has voltage detection function itself and an external control circuit 8″ is needed for detecting the voltage. Such technique has poor reliability in voltage detection and control. As a result, the actuator 1″ tends to operate too fast due to excessively high voltage. After a long period of use, the actuating member 3″ may rush out from a predetermined travel and get damaged. On the other hand, the actuator 1″ also may operate too slowly due to insufficient voltage. In this case, after a long period of use, the motor 2″ may overheat to cause damage of components.